Benign can also be used to describe a person who is kind and gentle: She has a benign personality. My last boss was mean and hateful. My current boss is very benign. In medicine, a benign tumor is the opposite of a malignant tumor. A malignant tumor is cancerous; a benign tumor is not.

Benevolent means to be for the purpose of doing good, such as a benevolent charity. Benign means gentle or non-harmful and is used mostly in medical terms, such as a benign tumor ( a tumor that is mostly harmless)

edit